Nutrition of the Ewe

A ewe's nutritional needs are not static; they vary largely with her stage
of production. For 16 to 20 weeks of the year, the ewe's energy needs are
very critical (such as during breeding, immediately before lambing, and
while lactating). Feed levels can be lowered to reduce the feed cost during
the early stages of gestation and when ewes are dry.

Maintenance of the ewe is generally thought of in terms of her nutritional
requirements when dry, because at that time her requirements are the lowest
of the year. However, wool production is a continuous process that must
be considered as part of the nutrient requirements throughout the year.

One of the most reliable sources of information regarding sheep nutrition
is The Nutrient Requirements of Sheep (sixth edition, 1985), which was
produced by the National Research Council (NRC). Table 3 illustrates the
requirements of sheep of different biological types and in different physiological
stages of production. Use the data only as guidelines, not as rigid standards.
In any flock, sheep are of different sizes and in different stages of production,
and it is not always possible to know at each feeding the exact nutrient
composition of the feed. However, if the producers follow the NRC guidelines,
the flock's nutritional requirements will be met as closely as scientifically
possible at this time.

The energy requirements are a function of the animal's basic metabolic
rate. However, several factors affect maintenance requirements.

Age. Yearlings tend to have about a 20 percent
higher energy requirement than adult sheep.This is probably due to the
yearling's additional requirements to support growth. This is of particular
importance to producers who breed ewes to lamb first at 12 to 18 months
of age.

Exercise. Grazing sheep may use from 10
to 100 percent more energy than do sheep in drylot conditions. However,
the magnitude of increase depends on the distance sheep must travel to
feed and water, and on the topography of the range.

Climate. Temperature, wind velocity, and
humidity can jointly affect energy requirements. The length and density
of the fleece also affects energy requirements. Wool plays an important
role in protecting sheep from both heat and cold. The insulating properties
of wool help to cool the sheep in the heat of summer and keep body temperatures
warmer in winter. Without wool, a sheep's energy requirements would be
higher.

Body Condition. It takes more feed to maintain
a fat sheep at a constant weight than it does a thin sheep. Keeping the
sheep excessively fat is not only expensive because of the feed, but also
it is detrimental to the ewe's reproductive capabilities and overall production
efficiency. A ewe should lose 5 to 7 percent of her body weight during
lactation and recover this weight loss during the dry period. Additionally,
the ewe should gain body weight during gestation in proportion to the weight
of the fetus and accompanying fluids.

In most sheep production situations, it is most economical to increase
body condition of the ewes during the nonlactation period and "milk it
off" in lactation, especially when low-cost pasture is available from early
to mid-gestation.

Reproduction Requirements. Reproductive
efficiency depends largely upon proper nutrition before and during the
breeding season. Large-bodied ewes tend to produce more lambs per ewe.
Do not confuse ewes of large size and scale with ewes that look large because
they are fat. Usually, excessively fat ewes have lower conception rates
and higher embryonic mortality. Furthermore, extremely poor body condition
is not conducive to efficient fertility and reproductive performance. Ewes
that have not had a properly balanced diet, including adequate phosphorus
and vitamin A, may have a poor lamb crop percentage.

Flushing. Flushing can improve the ewe's
body condition just before and during the breeding season. Generally, the
practice is thought to increase ovulation rate. Flushing has more effect
early in the breeding season. It is also beneficial late in the season,
as it tends to increase the opportunity for all ewes to become pregnant.
Flushing may be achieved by moving the ewes to a better pasture shortly
before breeding. The provision of a supplemental energy source (that is,
3/4 to 1 pound of whole corn per head per day) and(or) the introduction
of ewes to fresh pasture also can enhance the potential for ewes to respond
to flushing. The length of the flushing period can vary, but it probably
should begin 21 days before the breeding season and continue through one
estrous cycle (17 days) into the breeding season if possible.

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